In the mass production of beverages, it is usual to fill containers with a designated quantity of the beverage. A typical filling machine is therefore expected to control how much beverage is in the container.
One way to control the amount of beverage in a container is to weigh it as it is being filled. Another way is to fill it for a known time at a known volume-rate of flow. Yet another way is to introduce something analogous to a dipstick into the container so as to control the filling level. In these embodiments, it is important that there be a way to determine the filling level based on some interaction between the dipstick and the environment within the container's interior.